Abstract: The invention is directed to a method and apparatus for detecting an impact on a vehicle. The apparatus includes an acceleration sensor for sensing an acceleration of the vehicle, and a transformer for transforming the acceleration into an electric signal indicative of the acceleration to output an acceleration signal. A wavelet transformer transforms the acceleration signal by a wavelet function into a wavelet coefficient. The wavelet function is provided on the basis of a mother wavelet function localized in time, scaled in response to a scale parameter, and shifted in response to a shift parameter indicative of a time localization. Then, an impact determination device determines a condition of the impact on the basis of the wavelet coefficient with respect to at least a predetermined reference scale parameter. The apparatus may further include a vehicle passenger restraint system which restrains passengers in the vehicle in accordance with the result of determination by the impact determination device.